Ferritin Level Interpreter

What Ferritin Measures

Ferritin is an intracellular iron-storage protein found in virtually every cell of the body. Its primary role is to capture, store, and release iron in a regulated way, preventing free iron from generating harmful reactive oxygen species. A small amount of ferritin circulates in the bloodstream, and research suggests this serum ferritin level closely reflects the size of total body iron stores — which is why it is widely cited as a sensitive blood marker for detecting low iron stores.

Unlike haemoglobin, which research suggests only falls once iron stores are severely depleted, ferritin tends to decline as soon as iron reserves start to shrink. Studies indicate that low iron stores can be present for months before anaemia appears. A low ferritin may be associated with insufficient iron stores. Conversely, an elevated ferritin needs careful interpretation: because ferritin is also an acute-phase reactant — produced in larger quantities by the liver during inflammation, infection, or tissue injury — a high result does not automatically indicate iron overload.

Reference Ranges by Sex and Age

Sources: WHO (2020) Serum ferritin concentrations for the assessment of iron status and iron deficiency in populations; Mei Z et al., Lancet Haematol 2017; typical laboratory reference intervals.

Low Ferritin Without Anaemia

Research suggests that low iron stores without anaemia — also called pre-latent or latent iron deficiency — are commonly under-recognised. When ferritin falls between approximately 15 and 30 ng/mL, studies indicate that iron stores may be sufficiently depleted to affect cellular function and be associated with symptoms, even though haemoglobin may still be within the typical reference range. Symptoms reported in the literature include persistent fatigue, brain fog, hair shedding, cold hands and feet, poor exercise tolerance, restless legs, and brittle nails.

The WHO 2020 reference threshold for iron deficiency is ferritin below 15 ng/mL in adults. However, research by Mei Z et al. (Lancet Haematol, 2017) and others suggests that many individuals may experience functional iron deficiency at ferritin levels up to 30 ng/mL. Consensus thresholds in clinical practice typically suggest a practical functional threshold of 30 ng/mL, which many clinicians use to guide supplementation discussions, particularly in symptomatic individuals. Research suggests this under-recognition is especially common in pre-menopausal women, where low ferritin may be dismissed if haemoglobin appears within reference range.

Ferritin in Athletes

Research suggests endurance athletes may be disproportionately affected by low ferritin. Two mechanisms are commonly cited: exercise-induced hepcidin secretion — a hormone that may be released after prolonged exercise and which research suggests can reduce intestinal iron absorption for up to 24 hours — and foot-strike haemolysis, where repetitive impact may destroy red blood cells and accelerate iron losses. Studies indicate that sweat losses and gastrointestinal bleeding in runners may compound the problem. As a result, sports medicine practice commonly discusses ferritin targets above 40–50 ng/mL in endurance athletes, with some practitioners discussing >50 ng/mL in elite performers. These targets are widely cited in the sports medicine literature but are not established by a formal guideline body such as the WHO or a national haematology society. Athletes should discuss any specific targets with a qualified healthcare provider.

When Ferritin Is Elevated

A raised ferritin — particularly above 300 ng/mL in men or 200 ng/mL in women — may be associated with multiple different states. Common associations cited in the literature include: acute or chronic inflammation (including infections, autoimmune conditions, and cancer — ferritin is an acute-phase reactant and research suggests it can rise substantially without reflecting iron overload); non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH); excessive alcohol consumption; hereditary haemochromatosis (HFE gene variants associated with iron accumulation); hyperferritinaemia-cataract syndrome and other rare hyperferritinaemia syndromes; repeated blood transfusions; and recent intravenous iron administration. Consensus thresholds typically suggest that markedly elevated ferritin above 1,000 ng/mL warrants investigation for conditions such as haemochromatosis, hyperinflammatory states (including macrophage activation syndrome), or haematological malignancy. Because inflammation alone may elevate ferritin substantially, research suggests a high ferritin result should be interpreted alongside CRP (a marker of inflammation) and transferrin saturation (a measure of iron availability), not in isolation. Always discuss results with a qualified healthcare provider.

Restless Legs Syndrome and Ferritin

Research suggests iron plays a critical role in dopamine synthesis in the brain, and studies indicate that low brain iron — which may be reflected by low serum ferritin — is widely discussed as a contributor to Restless Legs Syndrome (RLS). The International Restless Legs Syndrome Study Group (IRLSSG) 2018 consensus suggests considering oral iron supplementation in RLS patients with serum ferritin at or below 75 ng/mL. For intravenous iron, the consensus threshold typically suggested is ferritin ≤75 ng/mL combined with a transferrin saturation below 20%. This threshold is notably higher than the general WHO reference threshold, which research suggests reflects the higher iron sensitivity of the dopaminergic system. Individuals with RLS and ferritin in the 30–75 ng/mL range whose values are otherwise within their lab reference range may benefit from a discussion of iron supplementation — this should be discussed with a qualified healthcare provider such as a neurologist or sleep medicine specialist.